This proposal will investigate a therapeutic approach to sensitize breast cancer (BC) cells and cancer stem cells (CSCc) to therapy in one of the most lethal forms of breast cancer, which is inflammatory breast cancer (IBC). IBC is highly aggressive and chemo/radiation resistant cancer in which cells invade the vascular and lymphatic systems via generation of tumor emboli; a process regulated by protein synthesis. Accordingly, this study seeks to study the chemo/radiosensitizing role of Ganoderma lucidum (Reishi) via protein synthesis regulation. In IBC the eukaryotic initiation factor, eIF4GI is overexpressed. eIF4GI reprograms protein synthesis of select mRNAs to increase IBC invasion, resistance to therapy of the BC and CSC population through the DNA damage response pathway, and cancer cell survival. We published that Reishi reduces global protein synthesis, cap-dependent translation, the expression of eIF4GI in IBC cells and tumors, and Reishi also induces cancer cell death. However the role of Reishi on sensitizing cells to therapy via modulation of eIF4GI in advanced BC or CSC has not been studied. Therefore, we hypothesize that Reishi sensitizes IBC cells and tumors to conventional therapy through protein synthesis regulation via eIF4GI. Specific aim 1 will evaluate the effects of Reishi on newly translated mRNAs via polysome profile analysis coupled to microarrays. We will also study newly synthesized proteins as well as evaluate the activity of cap-independent translation upon Reishi treatment. Specific aim 2 will study the effect of eIF4GI silencing to understand if Reishi sensitizes BC or CSC to radiation or chemotherapy via the DDR pathway. Silenced and non-silenced BC cells treated with Reishi, radiation or carboplatin then sorted for CSC isolation via CD44+/Cd24- and ALDH markers. DDR pathway will be assessed via immunoblots in all cells. Specific aim 3 will assess sensitization in vivo. Sorted CSC from IBC and advanced BC will be injected into SHO-SCID mice. Reishi will be orally gavaged daily, then irradiated or subject to carboplatin chemotherapy. In vivo imaging will assess tumor volume and micrometastases will be evaluated 6-8 weeks post-treatments. These studies will investigate the role of a medicinal mushroom with potential to sensitize to therapy targeting the synthesis of key proteins that play a role in the pathology of this intractable disease.